If you want to know how to get the biggest return on exertion in 2014, join the club or just stay in bed.

"The overall trend in fitness these days is efficiency," said Mark Beier, a fitness guru and creator of the quinoa-based Mark Bar (markbeier.com). "We just don't have time to work out. We have busy lives, juggling work, family and friends, and we often struggle to fit working out into the equation."

These are some of the ways people are doing it in 2014. And, yes, lingering in bed is one of them.

Bodyweight training

"One of the biggest fitness trends exploding in the industry right now is body weight training," said Beier, who integrates it into the classes he leads at Shred415 (shred415.com) in Chicago. "This type of workout literally uses just your own body as resistance."

You become the dumbbell, so to speak.

"You can manage to work out wherever you are, without the need for any equipment," Beier said.

While it appeals to minimalists, it's not just basic, boring reps of squats and lunges. Beier recommends a circuit of eight exercises that includes squats with a reverse lunge, forearm plank to palm pushups, V-ups and the dreaded burpees.

Quick HIIT fitness

"High intensity interval training (HIIT) is still going strong and remains the predominant trend for 2014," said Jenn Hogg, a group fitness manager for Equinox clubs (equinox.com).

A new at-home option in this genre is beachbody.com's P90X3, an abbreviated, 30-minute version of the original DVD workouts that have won devotees.

Or it can be as simple as running as fast as you can for 1 minute, then walking for 2 minutes, repeating that 3-minute interval five times. (Conduct an Internet search of "Tabata" for other options.)

Shape magazine says a mere 15 minutes of interval training, three times a week, can deliver better results than jogging on a treadmill for an hour. In addition to preserving muscle while burning fat, these workouts have been found to boost metabolism in the 24 hours afterward.

Integrated exertion

Rather than scheduling exercise, many are finding ways to distribute exercise over the course of their day, said Jay Cardiello, a celebrity trainer and nutrition expert (jcorebody.com).

He suggests sleeping in exercise clothes, then knocking out some pushups or planks when you wake, while still in bed. An unstable surface trains the body to fire up quickly, he said.

Other multitasking movements: Stand on one leg while brushing teeth or do squats to build muscles and improve balance while drying hair, or dance while getting dressed.

A bracelet that tracks exertion throughout the day (fitbit.com; nikefuelband.com) can be a good partner for this approach.

Fusion fitness

Katie Ann Rosen Kitchens, editor-in-chief for FabFitFun subscription fitness boxes (fabfitfun.com), expects fusion classes to build momentum. "There are so many hybrid yoga classes — aqua yoga, SUP yoga (stand-up yoga on a paddle board), YAS (yoga and spinning), Koga (kick boxing and yoga) — and people really like them. It's a great way to combine cardio, strength training and balance. We've also seen a huge increase in the number of cycle studios adding weight training to their workouts like SoulCycle, Cycle House and FlyWheel."

Mind-body fitness

The mindful living movement has expanded people's definition of what fitness is, said Marisa

Cerveris, a former New York City Ballet dancer, Pilates instructor and founder/designer of Steel Core yoga wear (available at Rodales.com).

"To maintain vitality throughout our lives, we must aspire to total fitness, which includes a clear mind and strong body," she said.

Nutritional needs of the brain will receive more attention, she said, as researchers continue to explore dietary connections to depression, ADHD, disease, low energy and brain fog.